SketchUp - 3D for Everyone
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
A360 VIEWER - Free online CAD Viewer
DraftSight - Discover Dassault Systèmes®' DRAFTSIGHT™ Professional CAD software that lets you create, edit, view and markup any kind of 2D drawing. Learn more here.
DXF View - A lightning-fast drawing viewer enables you to view DXF and DWG™ files on Mac